Signal optimization can significantly reduce congestion and improve traffic flow on arterial roads. However, when limited to traditional approaches, signal retiming projects take an average of eight hours to complete and many corridors are only retimed every 3-5 years.

The team of transportation engineers at DRMP were tasked with completing a signal retiming project in Escambia County. Using Miovision TrafficLink, they performed a corridor and intersection analysis, as well as a comprehensive signal retiming study, to optimize mainline progression and minimize overall signal delay along the corridor.

Using the Miovision Traffic Operations solution, DRMP proposed a number of recommendations that would help to optimize the mainline progression on N. Palafox St., and minimize overall signal delay along N. W Street. Their recommendations included that Escambia County should establish communication to the signal so the clocks at the two signals align to maintain coordination.

Following the completion of the retiming project, DRMP was able to show before-after results that helped Escambia County quantify the benefits of signal optimization, including:

• Saving time: Based on the vehicle travel time data collected, there is an estimated weekly time savings of approximately 1,200 vehicle hours along the corridor.
• Reducing fuel emissions: According to the Synchro model calculations, a significant weekly fuel savings of approximately 3,400 gallons would be realized.
• Reducing costs: The improvements translated to an estimated $7 million of cumulative delay, and fuel savings.

This study showed how small tweaks to the traffic network can have huge impacts to progression, fuel emissions, and costs. Using the Miovision TrafficLink system, DRMP will continue to monitor this intersection and make any modifications necessary to maintain or improve signal performance on an ongoing basis.

Study overview

Active Arterial Management / ATSPMs in practice:

According to the Florida Department of Transportation (FDOT), Active Arterial Management (AAM) is a program that addresses recurring or daily congestion and/or non-recurring congestion from incidents, taking into consideration the spill-over effect congestion can have on arterial roadways. The program also manages congestion relating to special events and work zones. Active Arterial Management includes active signal retiming, coordination with local responders, facilitation of emergency maintenance needs, and the dissemination of travel-related information through dynamic message signs. To be successful, active signal retiming and coordination requires inputs from the existing transportation infrastructure such as data from detectors, sensors, traffic controller telemetry, and phasing, and an organization of this data in a contextual way that spots traffic network inefficiencies through Automated Traffic Signal Performance Measures (ATSPMs). The program capitalizes on investments already made on the roadways, ports, signal systems, etc., by providing real-time traffic management. The goal is to reduce delays for all travelers, while improving congestion-related environmental factors such as air pollutants.

DRMP performed a corridor and intersection analysis, comprehensive signal retiming study, and Active Arterial Management services on N. Palafox Street and N. W Street in Escambia County, Florida. The overall purpose of the corridor analysis and signal retiming project was to optimize the mainline progression on N. Palafox St., and minimize overall signal delay on N. W Street. The N. Palafox arterial currently services approximately 105,000 vehicles per week within the retiming project area. Over the course of this study, eight traffic signals were analyzed, retimed, and coordinated along the 6.5 mile corridor from Hancock Lane on the south end of the project to E. Kingsfield Road on the north end of the project, as shown in Figure 1.

ATSPM equipment used for this study

The ATSPM equipment used for this study consisted of Miovision SmartLink with built-in WiFi MAC address capture for travel time, integration with the existing traffic controller to collect detector and phasing data, and the Miovision TrafficLink Performance Software that provides actionable ATSPM reports through an included web-based portal.

Miovision SmartLink

Miovision SmartLink is designed to make your existing traffic hardware smarter. Unlike expensive fiber optic cable, or generic cellular modems that just provide basic connectivity to the cabinet, SmartLink provides secure, LTE connectivity over VPN, and reads data from existing controllers and cabinet devices, transforming it into actionable insights.

Miovision Performance Software

Miovision Performance Software combines data collected from Miovision SmartLink including: telemetry, detector hits, phase intervals, timing plans, phase termination, volumes, pedestrian button usage, etc., combines them, and presents actionable ATSPMs through a series of customizable charts and graphs (split failures, split trends, PCD graphs, etc.) through the included web-based, Miovision TrafficLink portal.

Installation

The Miovision TrafficLink hardware was physically installed into the existing traffic cabinet infrastructure along the N. Palafox corridor between Hancock Lane and E. Kingsfield Road. Although the installation was completed during an off-peak demand period for this corridor, it was completed with no noticeable disruptions to progression of multimodal traffic along the corridor.

How DRPM collects ATSPM data for Active Arterial Management in Escambia County, Florida

]What started as a typical signal retiming project, evolved into an ongoing Active Arterial Management program. It began with DRMP collecting data and information on the pre-existing conditions of the intersections, such as turning movement counts, and signal timing data. This data provided direct inputs to the pre-existing traffic model. Using ATSPM data from the Miovision TrafficLink system, “before” traffic conditions – such as travel time and speed along different sections of the corridor – were collected. Using a combination of the data collected and optimization software, progression inefficiencies were uncovered and used to generate new timing plans for the corridor. To evaluate the performance of the new timing plans, ATSPMs were once again used to measure the impact of the signal retiming efforts. The major steps of the signal retiming project are summarized in Figure 2.

Using ATSPMs to spot traffic network inefficiencies

Considering that the Palafox corridor has a large volume of traffic with relatively low sidestreet volumes, the main objective of this study was to decrease travel times along Palafox St., using the ATSPM data. This would give the largest time savings to the most drivers.

DRMP used Miovision TrafficLink to collect key metrics from the intersection and generate ATSPM reports. Using the Miovision TrafficLink portal, DRMP used a series of analytics including; Time-Space diagram, Split Trends graph, Corridor Congestion scan, and Purdue Coordination Diagram to measure the before-and-after effects of signal timing and coordination changes along the corridor. This approach enables the user to verify that the offsets that were originally designed are actually happening in the corridor, and can also be used to verify the consistency of coordination.

The Time-Space diagram and Corridor Congestion Scans were used to get a clear understanding of the performance of the corridor in a single view. This view enabled the team to zoom in on where improvements could be made. Figure 3 below is the result from the Corridor Congestion Scan from November, 2018. The Corridor Congestion Scan uses travel time in each section of the corridor (vertical axis) on a 24-hour duration (horizontal axis) for both directions along the corridor. The median travel time data in each 15-minute duration is used to calculate the travel time index (TTI) using the definition from the FHWA. The TTI makes travel time along sections of the corridor with different lengths comparable. As can be observed, the TTI values range from 1 to 10 and visually from blue to red. The visual helps identify where and when the bottlenecks along the corridor are occurring.

Although the travel time index data provided through the Corridor Congestion Scan revealed potential areas of focus, on its own it provides no further context in identifying potential solutions. Therefore, other advanced ATSPMs such as Arrivals on Red, Purdue Coordination Diagram, and Time Space Diagrams were used to generate offset change recommendations to improve the travel times and speeds between these intersections along the corridor. After implementing the offset changes, speeds along the corridor immediately began to increase. The reduction in peak travel times are clear from the Corridor Congestion Scan below in Figure 4., below.

After adjusting signal timing offsets for optimal vehicle progression, the next step was to examine the performance of each individual movement throughout the day. This was done using the Split Trend Graphs in the TrafficLink portal. The Split Trend Graph provides a simple overview of the performance of a movement across a 24-hour duration using the occupancy information from the stopbar detectors.

The Miovision Time-Space diagram shown below, along the N. Palafox corridor tells a similar story of inefficient progression as measured before the signal timing changes were implemented. The blue/purple bands are a representation of progression efficiency. Efficient corridor progression would be represented by the blue/purple bands spanning the entire corridor. This indicates that the vehicles traveling along this corridor are arriving at each intersection at the green phase as expected. Shorter bands indicate vehicles arriving out-of-phase, which increases stopping and starting, as well as idling, and reduces overall efficiency.

Once the signal timing changes and coordinations were implemented, a reevaluation of corridor progression using the Miovision Time-Space diagram in the TrafficLink portal revealed significant improvements. As a result of the signal timing and coordination changes, a higher number of vehicles are now able to drive the length of the corridor with minimal stopping – greatly improving mobility and travel time for all vehicles, while reducing vehicle emissions from reduced idling.

Using the Occupancy Ratios, Split Failure Diagrams, and Split Trend Graphs, a pattern of split failures on many of the sidestreets was revealed from 2 pm to 4 pm.

There are several schools in the area which was causing an influx of traffic on and around bell times. In order to manage demand during these hours, a specific school timing plan was implemented between 2 pm and 4 pm in order to manage the demand. The signal phasing splits were adjusted to allocate more time to the side streets at all locations based on the ATSPM data, and improve the flow of traffic for everyone.

Using the ATSPM data – specifically the Split Trend Graph – the total number of split failures observed dropped dramatically, and the overall delay decreased as well. The continuous nature of accessing high-resolution data allowed for multiple iterations of adjusting the signal phasing splits at different times of day, while also ensuring that it isn’t negatively affecting the travel times or progression.

One of the unique aspects of this project was the continuous improvements to the traffic performance after the new signal timing plans were implemented. Active Arterial Management was done using Miovision TrafficLink on a monthly basis to allow for an increase to, and continuous optimal operation of the corridor. Below is an example of how the data was used to provide continuous value by DRMP to Escambia County.

Benefits of Active Arterial Management using ATSPMs

Following the completion of the retiming project, DRMP was able to show before-after results that helped Escambia County quantify the benefits of signal optimization, including:

• Saving time: Based on the vehicle travel time data collected, there is an estimated weekly time savings of approximately 1,200 vehicle hours along the corridor.
• Reducing fuel emissions: According to the Synchro model calculations, a significant weekly fuel savings of approximately 3,400 gallons would be realized.
• Reducing costs: The improvements translated to an estimated $7 million of cumulative delay, and fuel savings.

The project has also enabled DRMP to provide ongoing traffic management consulting and services to Escambia County, to promote data-driven decision making, and outcome-based results.

Conclusion

Although signal optimization can significantly reduce congestion and improve traffic flow on arterial roads, accessing the high-resolution data needed to spot inefficiencies and measure before-and-after impacts of your efforts can often be challenging.

ATSPMs add necessary context to individual data sets that assist traffic teams with their Active Arterial Management programs. As this study uncovered, traffic engineering firm DRMP worked with Escambia County in Florida to help them spot inefficiencies along a well-traveled corridor that also had a high concentration of schools in the area.

Using the Miovision Traffic Operations solution, DRMP proposed a number of recommendations that would help optimize the mainline progression and minimize overall signal delay along the arterials. Their recommendations included that Escambia County should establish communication to the signal so the clocks at the two signals align to maintain coordination.

Following the completion of the retiming project, DRMP were able to show before-after results that helped Escambia County quantify the benefits of signal optimization, including:

• Saving time: Based on the vehicle travel time data collected, there is an estimated weekly time savings of approximately 1,200 vehicle hours along the corridor.
• Reducing fuel emissions: According to the Synchro model calculations, a significant weekly fuel savings of approximately 3,400 gallons would be realized.
• Reducing costs: The improvements translated to an estimated $7 million of cumulative delay, and fuel savings.

This study showed how small tweaks to the traffic network can have huge impacts to progression, fuel emissions, and costs. Using the Miovision TrafficLink system, DRMP will continue to monitor this corridor, and will make any modifications necessary to maintain or improve signal performance on an on-going basis.